How to put a transparent texture over a material in the blender render?
Quite easy. After you set up your base material (in my case a blue color) go over to the Texture tab.

Add in the texture (it doesn't even need to have an alpha channel).
Now set the Image Mapping to Clip, if you don't the image will tile all over your object. (Do note that the clip option does not work with the Texture or Material shading in the 3D view, you have to be in rendered mode.)
Set the Mapping to UV, it is one of the easiest ways to do a decal type of texture.
Last, do not have this texture influence the alpha at all. The only thing this texture should Influence is the Color.


That's it. Where the texture is, and is not transparent, the texture is displayed; everywhere else the material is displayed.


This is what my material with the texture settings above looks like. The blender logo is a png with an alpha channel, the blue is from my diffuse color in the material.